The present invention is a surgical device for setting fractured bones, such as connecting the fractured neck of a femur bone to its shaft with screws by means of a pre-drilled connector plate, without requiring a large incision to be made in the overlying skin and tissue. In particular, a new screwdriver is provided, together with a technique for its use, that improve the ease and reliability with which the screws are inserted and the fractured bone set.
The present invention is an improvement of my U.S. Pat. Nos. 4,465,065 and 5,429,641. The subject matter of both patents is hereby incorporated by reference. Only those features of both patents are summarized below as are deemed helpful in explaining the structure, operation, need for and advantages of the present invention. A complete and thorough explanation of all the features of those patents can be gained, of course, from a direct reading thereof.
In U.S. Pat. No. 4,465,065 the connector plate has a sharp lower edge by which it penetrates through a small incision in the trochanter region into close contact with the shaft. During the operation the plate is temporarily attached to the horizontal portion of a connector arm, while the vertical portion of the connector arm extends parallel to the connector plate and is provided with holes which are coaxial with the holes in the plate. Concentric inner and outer guide tubes are inserted through the holes in the vertical portion of the connector arm, are pushed through the soft tissue up to the plate and serve as guides for pre-drilling of the bone parts in the correct position as viewed by X-ray equipment. After such pre-drilling, the inner guide tubes are removed and the outer tubes serve for guiding the insertion of long screws, and are afterwards removed. The long screws are tightened so as to compress the fracture. The plate is secured to the femur shaft with short screws, and the connector arm is then detached from the plate, and the wound is closed.
The device disclosed in U.S. Pat. No. 5,429,641 serves the same purpose as and has many features in common with the above-described device, but is designed to avoid certain of its drawbacks which came to light during its use in surgical operations (xe2x80x9coperationsxe2x80x9d hereinafter) of the kind referred to.
In particular, U.S. Pat. No. 5,429,641 discloses a screw-and-sleeve assembly in which each long screw is axially movable within an associated sleeve that has a screw-threaded end that is firmly connected to a threaded bore in the connector plate. This feature permits active compression of the fracture by the surgeon and avoids a drawback of the above-described invention involving a gradual protrusion of the screw heads into the soft tissue causing subsequent irritation and pain to the patient.
Before going into its constructional details, it should be noted that the following directional expressions will be employed in respect of the femur bone, the connector plate, the screws and the related components of the surgical device. The expressions xe2x80x9ctopxe2x80x9d and xe2x80x9cupper portionxe2x80x9d of any part will refer to the femur top, and the xe2x80x9cbottomxe2x80x9d or xe2x80x9clower portionxe2x80x9d will refer to the direction towards the knee joint. The expression xe2x80x9cinsidexe2x80x9d or xe2x80x9cinnerxe2x80x9d will refer to parts close to the bone or pointing towards it, while the expression xe2x80x9coutsidexe2x80x9d or xe2x80x9couterxe2x80x9d will refer to those parts which are outside the human body being operated on, or pointing away from the bone.
The surgical device of U.S. Pat. No. 5,429,641 includes the following components.
Components Which are to Remain in the Body After the Operation is Completed:
1. A connector plate I.
2. Two long screws II used for connecting the fractured parts to the connector plate.
3. Two or more short screws 33 securing the lower plate portion to the femur shaft.
B. Auxiliary Equipment for Insertion and Fixation of the Permanent Components:
1. An angular connector arm IV.
2. Two long inner and outer guide tubes of a length sufficient to extend from the bores in the connector arm to the corresponding oblique bores in the connector plate. Outer guide tube 31 has an inner diameter corresponding to the diameter of the screw to be inserted and to be screwed into the fractured bone. Two inner, removable and alternately insertable guide tubes, are provided. Tube 32 is used first. It is concentrically bored to the diameter of a guide wire 30 to be pushed therethrough into the bone. After tube 32 has served its purpose and is removed, second tube 32a is used. It is concentrically bored to the diameter of a drill bit 35 adapted to pre-drill the femur bone for reception of the two screw-and-sleeve assemblies which include the long screws. The diameter of the pre-drilled bore in the femur accommodates the sleeve therein.
3. Two or more shorter guide tubes (not shown) for pre-drilling bone before final insertion of the short screws for firm attachment of the connector plate to the femur shaft.
4. A special screwdriver V adapted for manipulating the long screws and their sleeves to fix the sleeves to the connector plate, to insert the screws into the fractured bone, and to compress the fracture.
The auxiliary equipment is removed from the body after the connector plate has been firmly connected to the femur shaft with the short screws and long screws, and the fracture has been connected and duly compressed by means of the long screws, whereafter the wounds are to be dressed.
The connector plate I of substantially rectangular cross section illustrated in FIG. 1 includes a straight lower, main portion 1 and a head portion 2 outwardly bent in respect of the main portion, to conform to the contour of the bone. Next to the head portion, two obliquely-directed, screw-threaded bores 5 penetrate the main portion at an angle of about 130xc2x0, the outer surface of the main portion being thickened by two lugs 6 permitting a greater length of the bores 5. The lower end 8 of the main portion is sharpened for the purpose of penetrating through the soft tissue and muscles close to the femur shaft during insertion of the connector plate through a small cut in the skin into its final position where it is attached to the bone with short screws.
An assembly of a long screw II and its relatively short sleeve III is illustrated in FIG. 2, and details of both are shown in FIGS. 3 and 4. The screw includes a relatively long shaft 10, an inner end 10a provided with screw thread 11 similar to that provided on wood screws, and an outer end 10b having a coaxial recess 12 formed therein in the shape of a hexagon that is axially extended with a screw-threaded bore 13 of a smaller diameter. The outer end 10b of the screw is slidably, but firmly, movable lengthwise and rotatably within the inner bore of sleeve body 14, which has its outer end 14b provided with outside screw thread 15 and slotted by two or four slots 16 serving to engage the screwdriver V. The inner end 14a of the sleeve III is inwardly crimped slightly, thereby preventing the screw II from sliding out of the sleeve by contact with a step 17 on the screw shaft.
FIGS. 5-10 illustrate the auxiliary equipment serving for inserting and tightening long screws II and for compressing the fracture by bringing the bone parts toward each other after insertion of the screws is completed. The main component is an L-shaped connector arm IV which includes a horizontal portion 20 and a vertical portion 21 firmly connected to each other at right angles. The vertical portion 21 contains two large, obliquely-directed bores 26 which are coaxially aligned with the bores 5 in the connector plate, but are of a larger diameter for permitting the passage and fixation of the guide tubes.
FIG. 5 illustrates an early stage of a surgical operation performed with the above-described device. After the connector plate I has been manually inserted by the surgeon into the thigh through a small cut and has been slid into an approximate position while being viewed by means of X-ray equipment, its correct and precise location in relation to the neck of the femur is found by means of a guide wire 30 which is inserted into the bone of the femur upper shaft and into the bone of the femur neck through inner guide tube 32 located within outer tube 31 extending from the bore 26 of the connector arm to the screw-threaded bore 5 of the connector plate. The tip of guide wire 30 is a diamond bit, and the guide wire is rotated by a handheld type of power tool (not shown) which is well known and, thus, its details are not deemed necessary.
The inner guide tube 32 is screwed into bore 5 of the plate in order to permit exact centering of guide wire 30 and to prevent its inadvertent disengagement from the connector plate. In case connector plate I is not yet in the correct location, the guide wire 30 is withdrawn, the connector plate is moved by means of the connector arm into another position and the guide wire 30 is again inserted into the bone. If the location is found to be correct as seen on an X-ray image, the connector plate is fixed to the bone in this position, whereupon the guide wire 30 and the inner tubular guide (32) are removed. Outer tube 31 is meanwhile held in place by a set screw (not shown in FIG. 5 but identified as 28 in FIG. 9 of U.S. Pat. No. 5,429,641). Then, inner guide tube 32 is replaced within outer tube 31 by the second inner guide tube 32a having a wider inner bore than tube 32 (see FIG. 7), in order to accommodate drill bit 35 which is inserted therethrough for the purpose of pre-drilling the bone prior to use of the long screws.
With a mechanical rotation of drill bit 35 by the above-mentioned power tool, a hole is drilled through the upper femur shaft and into the lower part, or base, of the neck for subsequent insertion thereinto of a long screw. Such pre-drilling provides room in the bone to (as explained below in connection with subsequent steps) receive sleeve III while the threaded tip of the long screw, which is self-cutting, drills its way into the bone without pre-drilling. Since the diameter of drill bit 35 is preferably smaller than the diameter of sleeve III, the pre-drilling is done in two stages, with use of drill bit 35 being followed by another drill bit (not shown) having a diameter corresponding to that of sleeve III.
The screwdriver V is illustrated in FIGS. 8-10. It comprises the following three concentrically aligned shafts which are independently movable in both axial and rotary directions:
1. An innermost shaft 40 has a screw-threaded end 41 suitable for engaging the bore 13 in the outer end 10b of the long screw II. Shaft 40 is rotatable and longitudinally movable by a handle 42 at the outer end of the screw driver.
2. An intermediate tubular shaft 43 has a hexagon-shaped inner end 44 adapted for driving engagement with the hexagonal-shaped recess 12 in the long screw II. Rotation of shaft 43 is used to drive the screw into the pre-drilled bone. Shaft 43 is rotated by cylindrical handle 45 coupled thereto via a disc 46 firmly mounted on the shaft 43.
3. An outermost tubular shaft 47 has an inner end in the form of cross-wise aligned edges 48 for engagement with slots 16 in the sleeve III. Shaft 47 is rotatable by means of a cylindrical handle 49 for the purpose of screwing sleeves III into the connector plate I.
An outer sleeve 56 is rotationally and longitudinally movable on the intermediate shaft 43. Sleeve 56 is provided with a circumferential recess 58 engaged by a pin 59 serving to limit the longitudinal motion of shaft 47. A second circumferential recess (unnumbered) is provided at the other end of sleeve 56 and engages a stop 57.
The above-described components can be axially moved relative to each other, but are urged into their normal position by helical springs 50 and 51. Additional axial motion of the tubular shaft 43 is made possible by withdrawal of stop 57 from its associated recess for a specific use that will be explained below.
After the bone has been pre-drilled in alignment with the oblique bores 26, the inner tubular guide 32a is removed. Then, as illustrated in FIG. 6, the two screw-and-sleeve assemblies are inserted and fastened, one after the other, with the aid of the screw driver V, as follows. A long screw II is retracted into its sleeve III and positioned so that its outer end 10b can be engaged by screwdriver V. The hexagon-shaped end 44 of the screwdriver is pushed into the correspondingly shaped recess 12 in the outer end 10b of the screw. By rotating handle 42 and pushing it against the force of helical spring 51, the threaded end 41 of the innermost shaft 40 of the screw-driver is screwed into screw-threaded bore 13 of the screw, while the protruding edges 48 of the outermost tubular shaft 47 are urged into slots 16 in the end of sleeve III by means of helical spring 50. Additional tightening of the threaded end 41 into bore 13 connects and firmly secures the screw-and-sleeve assembly to the screwdriver V.
By means of the screwdriver V, the screw-and-sleeve assembly is pushed in an inward direction through the outer tubular guide 31, and rotated as far as the screw-thread 15 on the sleeve III allows. With rotation of handle 49 the sleeve is screwed into bore 5 of the connector plate. By pulling out the stop 57, handle 45 which is connected to the inner shaft 43 by means of collar 46, can be moved in an inward direction thereby pushing shaft 43 inwardly. By rotating and pushing handle 45 inwardly, screw II is moved relative to sleeve III. More specifically, the outer end 10b travels within sleeve body 14 as threaded inner end 10a and shaft 10 extend therefrom while being urged through the femoral neck into the head portion. The threaded inner end 10a enters into the pre-drilled bore in the femur bone and continues being screwed more deeply thereinto as handle 45 is turned manually by the surgeon.
Rotation of handle 45 is stopped as soon as the screw II has reached the required depth in the femur head as viewed by X-ray equipment, or whenever step 17 on the screw has reached the crimped inner end 14a of the sleeve (see FIG. 2). A pin 60 engaged within a circumferential groove 61 limits the distance to which handle 42 can be moved in an outward direction, while being urged there by spring 51. In addition, during fracture compression (as explained below) pin 60 transfers the load from handle 45 to shaft 40 via handle 42.
In order to pull the fractured head in the direction of the femur shaft and, thus, to compress the fracture, a retracting device VI is attached to the handles 45 and 49 of screwdriver V by means of pins 52 inserted into corresponding holes 53. By rotating the handwheel 54, screw 55 pulls handles 49 and 45 apart. Since the position of handle 49 is fixed relative to the connector plate, this produces outward motion of handle 45. Such outward motion of handle 45 is transferred to handle 42 (by means of pin 60), thereby pulling (via shaft 40) the attached screw II (via threaded end 41 screwed into hole 13) outwardly and into the sleeve III which is firmly screwed and secured to the connector plate. Opposing surfaces at the fracture site have interdigitating spikes which engage when the fracture is sufficiently compressed. This maintains the compression even after the pull created by the screwdriver is released. Muscle pull and weight-bearing also help to maintain this compression. After insertion and fixation of the first screw, the second screw is inserted into the fractured bone parts in the same manner.
With insertion of both long screws as described above, and also of the short screws, the connector plate I is firmly attached to the femur shaft. The connector arm is then removed from the plate and out of the body, the skin incisions are closed, and the wounds are dressed.
A disadvantage of the surgical device disclosed in U.S. Pat. No. 5,429,641 arises from the fact that the screw-and-sleeve assembly is moved through guide tube 31 while outer end 10b of long screw II is at outer end 14b of sleeve III. Since screw II is considerably longer than sleeve III, the threaded tip at inner end 10a of screw II will initially bite into the bone (beyond the pre-drilled bore in the femur) before thread 15 of sleeve III threadedly engages tapped bore 5. Any minute deflection of screw II from perfect alignment will prevent thread 15 from engaging tapped bore 5. For example, the longest contemplated length for screw II is 118 mm and the length of sleeve III is 42 mm. In order for the threaded portion 15 of sleeve III to reach bore 5, it is necessary for the tip of screw II to bite into the bone by a distance of up to 82 mm. It has been found in practice that despite the precise alignment achieved by the pre-drilling operation as described above, when screw II bites into the bone, certain minute lateral deflections from the perfect alignment can occur. Even such minute deflections can prevent the threaded portion 15 on sleeve III from threadedly engaging tapped bore 5. If this occurs, then it becomes impossible to secure sleeve III to connector plate I. This may result in loosening sleeve III outwardly into the soft tissue.
Such a situation is not tolerable. Consequently, the surgeon must reposition the device by repeating the above-described steps until the correct path is found. This is time consuming and prolongs the surgical operation.
One object of the present invention is to provide a surgical device for setting bones that avoids the possibility of a misalignment which prevents engagement between threaded portion 15 of sleeve III and tapped bore 5 of connector plate I.
Another object of the present invention is to simplify the special screwdriver for easier surgical use and cleaning.
A further object of the present invention is to reduce the manufacturing cost of the special screwdriver.
These and other objects are attained in accordance with one aspect of the present invention directed to an improved screwdriver for use as part of auxiliary equipment serving to insert and connect a surgical device for percutaneous connection of a fractured upper part of a femur to a femur shaft of a patient, wherein the surgical device comprises the following components to remain in the body of the patient: (a) a bar-shaped plate having an axis, an inner surface to be placed onto the femur, an outer surface, a head portion and a bottom provided with a sharpened end for insertion of the bar-shaped plate through a small incision in the skin of the patient, the bar-shaped plate being provided in a lower portion thereof with at least two countersunk, through-going bores and in an upper portion thereof with two adjoining oblique, screw-threaded bores directed in an upward direction at an angle of about 130xc2x0, a screw-threaded bore perpendicular to the axis of the bar-shaped plate being provided in the head portion, (b) two long screws, each screw having a straight shaft, a wood-screw-shaped inner end for insertion into the fractured upper part of the femur and an outer end coaxially recessed with a polygonal shape, the recess being continued by a screw-threaded bore concentric with an axis of the shaft, (c) a sleeve of a shorter length than the screw, with the outer end of the screw being positioned in the sleeve in a manner so as to be movable in both axial and rotational directions in the sleeve, the sleeve having an outer end provided with a screw-thread corresponding to the screw thread in the oblique bores in the bar-shaped plate such that the sleeve is threadedly engageable within the oblique bores, the sleeve further having at least two recesses for engagement of a screwdriver, and (d) at least two shorter screws for securing the bar-shaped plate to the femur shaft, the at least two shorter screws extending through the countersunk, through-going bores into bone material of the femur shaft. The auxiliary equipment comprises: (a) an angular connector arm including a short horizontal portion for connection to the head portion of the bar-shaped plate and a longer vertical portion extending parallel to the lower portion of the bar-shaped plate, wherein the horizontal portion is provided with an axial perforation for passage of a screw engaging with the screw-threaded bore in the head portion of the bar-shaped plate and is shaped to conform to the shape of the head portion to ensure absolute parallelism of the vertical portion with the bar-shaped plate, and wherein the vertical portion is provided with two adjoining obliquely directed bores coaxially aligned with the two oblique screw-threaded bores in the plate, and with at least two straight bores coaxially aligned with the at least two countersunk, through-going bores in the plate, (b) a first tubular guide of an outer diameter cooperating with the oblique bores in the angular connector arm and of an inner diameter corresponding to an outer diameter of the sleeve covering the long screw, of a length compatible with a distance between the respective oblique bores in the plate and the angular connector arm, (c) a first removable tube for insertion into the first tubular guide and having a bore with an inner diameter corresponding to an outer diameter of a guide wire to be pushed therethrough into the fractured upper part, (d) a second removable tube for insertion into the first tubular guide and having a bore with an inner diameter corresponding to a diameter of a drill to provide a pre-drilled portion of the femur sized to accommodate the sleeve therein; (e) a guide wire to be pushed through the bore in the first removable tube, (f) a drill to be inserted into the bone material through the bore in the second removable tube, (g) a second tubular guide for insertion into the straight bores in the angular connector arm, of a length compatible with the distance to the bar-shaped plate, and of an inner diameter corresponding to an outer diameter of the shorter screws, and (h) a screwdriver for insertion and fixation of the long screws. The screwdriver includes: (a) an inner shaft provided with a screw-threaded inner end for engagement with the screw-threaded bore in the recessed end of the long screw, (b) an intermediate shaft provided with a polygonal inner end for engagement with the polygonal recess in the long screw to drive the long screw into the upper part of the femur by applying rotational and inwardly directed forces so that the wood-screw shaped inner end bites into the upper part of the femur, and (c) an outer shaft provided at an inner end thereof with protruding teeth for engagement with the recesses in the sleeve, wherein the screwdriver is provided with means for pulling the long screw in an outward direction relative to the sleeve, all of the inner, intermediate and outer shafts being independently movable in both axial and rotational directions by handles attached to outer ends thereof, and resilient components are provided to adjust axial alignment of the respective shafts relative to each other.
The improvement in the screwdriver comprises: (a) force-applying means for pulling a section of the long screw by the inner shaft engaged therewith into the outer shaft to have only a length of the long screw protruding inwardly of the sleeve such that the screw-thread on the outer end of the sleeve can be threadedly engaged with each one of the screw-threaded oblique bores in the connector plate before the inner end of the long screw is driven to bite into the femur past the pre-drilled portion, and (b) means in the outer shaft to accommodate therein the section of the long screw.
In accordance with another aspect of the present invention, an improved screwdriver is provided which is used during surgery for re-joining two pieces of a fractured bone in cooperation with a connector plate adapted to be secured to a first one of the two bone pieces. The connector plate has at least one screw-threaded bore with its axis being directed at a second of the bone pieces through a pre-drilled portion of the first bone piece. A screw is provided having a screw-shaped inner end for, as the screw is driven with forceful rotation, initially biting into the bone upon passing through the bore of the connector plate and out of the pre-drilled portion of the first bone piece, the screw having an outer end adapted to be engaged with the screwdriver. A sleeve is provided of a shorter length than the screw which is axially movable and rotatable on the screw, the sleeve having an outer end provided with a screw thread corresponding to the screw thread in the bore of the connector plate for threaded engagement therewith. The screwdriver comprises: a first shaft unit with engaging means at its inner end for engaging the first shaft unit with the screw to move the screw axially and to rotate the screw; a second shaft unit axially movable and rotatable relative to the first shaft unit and having rotation means at its inner end for rotating the sleeve; and motive means for effecting axial movement of the first shaft unit for moving the screw engaged therewith outward relative to the sleeve so that the outer end of the screw passes through the sleeve and into the second shaft unit to a position therein such that the inner end of the screw protrudes inwardly from the inner end of the sleeve by a length such that the threaded outer end of the sleeve can be threadedly engaged with the bore of the connector plate before the screw is driven to have the inner end of the screw initially bite into the bone beyond the pre-drilled portion.
Yet another aspect of the present invention is directed to an improved screwdriver used during surgery for re-joining two pieces of a fractured bone in cooperation with the above-described connector plate, and screw-and-sleeve assembly. The screwdriver comprises: a first shaft unit having a screw-threaded tip at its inner end corresponding to a screw-threaded bore in the screw for threaded engagement therewith, the first shaft unit further comprising a polygon-shaped portion at its inner end corresponding to and drivingly engageable in a polygon-shaped recess in the screw; a second shaft unit axially movable and rotatable relative to the first shaft unit and having a transverse edge at its inner end corresponding to and drivingly engageable in a slot on the outer end of the sleeve; a first handle unit attached to the outer end of the first shaft unit, the first handle unit being coupled to the screw as the screw-threaded tip of the first shaft unit is threadedly engaged in the screw-threaded bore of the screw, whereby the screw is movable axially with axial movement of the first handle unit, and whereby the screw is rotatable with rotational motion of the first handle unit; and a second handle unit attached to the outer end of the second shaft unit, the second handle unit being coupled to the sleeve as the transverse edge at the inner end of the second shaft unit is positioned within the slot on the outer end of the sleeve, whereby the sleeve is rotatable and axially movable with respective rotation and axial motion of the second handle unit; the second shaft unit being sized to accommodate therein a portion of the screw which is defined by moving the screw outward relative to the sleeve so that the outer end of the screw passes through the sleeve and into the second shaft unit to a position therein such that the inner end of the screw protrudes inwardly from the inner end of the sleeve by only a length such that the threaded outer end of the sleeve can be threadedly engaged with the bore of the connector plate before the screw is driven to have the inner end of the screw initially bite into the bone beyond the pre-drilled portion.
One further aspect of the present invention is directed to an improved screwdriver used during surgery for re-joining two pieces of a fractured bone in cooperation with the above-described connector plate, and screw-and-sleeve assembly. The screwdriver comprises: a first shaft unit having a screw-threaded tip at its inner end corresponding to a screw-threaded bore in the screw for threaded engagement therewith, the first shaft unit further comprising a polygon-shaped portion at its inner end corresponding to and drivingly engageable in a polygon-shaped recess in the screw; a second shaft unit axially movable and rotatable relative to the first shaft unit and having a transverse edge at its inner end corresponding to and drivingly engageable in a slot on the outer end of the sleeve; a first handle unit attached to the outer end of the first shaft unit, the handle being coupled to the screw as the screw-threaded tip of the first shaft unit is threadedly engaged in the screw-threaded bore of the screw, whereby the screw is movable axially with axial movement of the first-handle unit, and whereby the screw is rotatable with rotational motion of the first handle unit; a second handle unit attached to the outer end of the second shaft unit, the second handle unit being coupled to the sleeve as the transverse edge at the inner end of the second shaft unit is positioned within the slot on the outer end of the sleeve, whereby the sleeve is rotatable and axially movable with respective rotation and axial motion of the second handle unit; and a force-receptive element integral to the first shaft unit and a force applying member drivingly engageable with the force-receptive element to move at least one of the first and second shaft units axially with respect to each.
A still further aspect of the present invention is directed to an improved screwdriver used during surgery for re-joining two pieces of a fractured bone in cooperation with the above-described connector plate, and screw-and-sleeve assembly. The screwdriver comprises: a first shaft unit with engaging means at its inner end for engaging the first shaft unit with the screw to move the screw axially and to rotate the screw; a second shaft unit axially movable and rotatable relative to the first shaft unit and having rotation means at its inner end for rotating the sleeve; and a force-receptive element integral to the first shaft unit and a force applying member drivingly engageable with the force-receptive element to move at least one of the first and second shaft units axially with respect to each.
One other aspect of the present invention is directed to a method for operating a screwdriver in connection with surgery for re-joining two pieces of a fractured bone in cooperation with the above-described connector plate, and screw-and-sleeve assembly. The screwdriver includes first and second shaft units axially and rotatably movable relative to each other. The method of operating the screwdriver comprises: engaging an inner end of the first shaft unit with the screw; engaging an inner end of the second shaft unit with the sleeve; and moving the first shaft unit to effect axial outward movement of the screw relative to the sleeve so that the outer end of the screw passes out of the sleeve and is accommodated within the second shaft unit at a position such that the inner end of the screw protrudes inwardly from the inner end of the sleeve by a length such that the threaded outer end of the sleeve can be threadedly engaged with the bore of the connector plate before the screw is driven to have the inner end of the screw initially bite into the bone beyond the pre-drilled portion.
Still another aspect of the present invention is directed to a method for operating a screwdriver in connection with surgery for re-joining two pieces of a fractured bone in cooperation with the above-described connector plate, and screw-and-sleeve assembly. The screwdriver includes first and second shaft units axially and rotatably movable relative to each other, and a force-receptive element integral to the first shaft unit and a force applying member drivingly engageable with the force-receptive element to move at least one of the first and second shaft units axially with respect to each. The method of operating the screwdriver comprises: engaging an inner end of the first shaft unit with the screw; engaging an inner end of the second shaft unit with the sleeve; and actuating the force applying member drivingly engaged with the force-receptive element to move at least one of the first and second shaft units axially with respect to the other.